The objective of this research is to determine whether significant advantage can be achieved in internal fixation of diaphyseal fractures through the use of internal fixation plates of improved design. We wish to test the hypothesis that internal fixation plates of reduced stiffness are superior with respect to the late complication of stress protection induced osteopenia as commonly observed with traditional fracture management using sturdy metal plates. We have shown advantages existed with respect to biomechanical properties of canine radii and femora internally fixed with a plate of reduced bending and axial stiffness by a factor of 10. These results were confirmed by quantitative histological measurements. At present we are using combined bench testing experiments, as well as advanced numerical analysis techniques (finite element method) to evaluate the optimal values of axial, bending and torsional stiffness for the internal fixation plate. The newly designed plate will provide adequate fixation with respect to the accomplishment of fracture healing, as well as minimize the osteopenia following fracture healing during bone remodeling. The techniques of evaluation in this study will include periodic X-ray to study the progress of fracture healing of mid-shaft canine femoral osteotomies, nondestructive and destructive bioengineering tests, quantitative histological measurements using UV light microscopy to quantify the tetracycline labeled new bone and porosity, as well as microradiography. The results of an optimally designed plate will be compared with the traditional internal fixation devices.